Glioblastoma (GBM) is the most common primary brain tumor, and among the most lethal human cancers. No cure exists, and only limited treatment advances have been achieved. A highly promising area of immunotherapy is adoptive transfer of genetically engineered, patient-derived blood lymphocytes transfected with chimeric antigen receptor genes (CARs) to target and destroy cancer cells, currently being explored for treating GBM. Critical challenges to using CAR-modified T (CART) cells involve dose-limiting immunotoxicities including cytokine-release-syndrome (CRS) and neurological toxicities. Most research has aimed at improving CART efficacy, while the mechanisms of toxicities/adverse reactions, innovative strategies for their management, and their implications for anti-tumor efficacy remain under-explored. I recently discovered that endogenous catecholamines drive CART-induced CRS, via a self-amplifying feed-forward loop in immune cells, and that inhibiting their production protected CART-treated Raji lymphoma-bearing xenograft mice from lethal CRS and enhanced tumor eradication, suggesting separate pathways of immunotoxicity and anti-tumor response. The goal of this proposal is to elucidate the mechanism by which catecholamines mediate immunotoxicity in CART therapy in brain tumors and other cancers and assess their impact on the anti-tumor response in immunocompetent cancer models. My central hypothesis is that catecholamines promote CART- induced CRS and that its pharmacologic inhibition improves CART therapy safety and tumor-specific killing. I will test this idea in 3 Specific Aims: 1) Evaluate the induction of catecholamines and CRS in an immunocompetent CD19+ B cell ALL CART19 model, and determine the dual impact of suppressing catecholamine production on cytokine release and anti-tumor responses, by analyzing catecholamine and cytokine release in a CD19+ B cell ALL CART19 model, which recapitulates the CRS seen in human CART19 therapy; 2) Determine the signaling pathway by which catecholamines upregulate catecholamine production and cytokine release in mouse CART19 (mCART19) therapy and how this affects CART functionality, by using gene expression microarray and pathway reporter arrays to discover contributing mechanisms of epinephrine- induced catecholamine and cytokine synthesis and by determining the effects of cytokines most significantly altered on mCART19 cell activation, expansion and cytotoxicity; 3) Determine whether blocking endogenous catecholamine synthesis reduces CART-induced systemic and CNS immunotoxicity and improves anti-tumor responses in an immunocompetent mouse GBM model. The results will advance basic understanding of endogenous pathways contributing to immunotoxicity, and may enable improved outcomes of CART therapy and management of adverse immunotoxicities, via new insights into their mechanisms and a novel treatment strategy of catecholamine blockade, which inhibits multiple cytokines more broadly than anti-IL6R antibody (tocilizumab).